In everyday perception, we seamlessly fuse information from multiple senses (e.g. sight, hearing, touch) to discern and identify objects in the world around us. My long-term goal is to understand the neural bases of multisensory integration and their relationship to perception. While recent discoveries inform us that vibrotactile stimuli can augment what people hear and indicate that touch and sound may be integrated early in the sensory processing stream, the precise anatomical circuitry and physiological mechanisms of this phenomenon are unknown. Specifically, it is unknown whether the impact of vibrotactile stimuli on auditory cortical processing utilizes feedforward or feedback circuits in primary and non-primary areas and to what extent vibrotactile inputs operate by modulating auditory neuron excitability, as opposed to causing direct (additive) excitation of auditory neurons. The current application will address these questions by characterizing how vibrotactile inputs impact on the discriminative processing of sounds in auditory cortex. I will record neuronal activity from depth electrodes placed in primary and non-primary auditory cortices of awake monkeys while they are performing auditory discriminations. Conditions will include auditory-alone, vibratory-alone and combined stimulation. To help in defining the physiology of multisensory interactions, I will vary the intensity of the auditory stimulus and the asynchrony between vibratory and auditory stimuli. Analysis of the laminar profile and timing of sensory inputs into the cortical layers will help to define effects due to feedforward versus feedback circuitry. Analysis of somato-auditory interactions as a function of stimulus manipulations will help to determine whether vibratory effects are "modulatory" versus "directly excitatory," and also whether vibro- auditory interactions in auditory cortex adhere to recognized principles of multisensory integration. The monkey studies in our laboratory at Nathan Kline Institute are tightly integrated with ongoing EEC and fMRI studies in patients with schizophrenia conducted within our division (Cognitive Neuroscience and Schizophrenia Program), and in cooperation with the Rockland Psychiatric Center, an in-patient New York State facility for severe and complex mental illness. In particular, recent evidence shows that schizophrenic patients exhibit reduced or distorted multisensory integration, and animal models provide the best and often the only methods for research into the neuronal mechanics of these essential processes. The proposed research thus directly contributes to ongoing investigation of multisensory integration dysfunctions in patients with schizophrenia.